Bodhisattva:
One whose essence is enlightenment; a being that compassionately refrains from entering nirvana in order to save others and is worshiped as a deity in Mahayana Buddhism
Buddha:
A person who has attained the state of perfect enlightenment sought in Buddhism.
The Buddha:
Indian philosopher & founder of Buddhism who formulated and taught doctrine of "four noble truths" and "chain of causation; Siddartha Gautama; Gautama Buddha.
Sangha:
Buddhist monastic order, traditionally composed of four groups: monks, nuns, laymen, and laywomen.
Samsara:
The indefinitely repeated cycles of birth, misery, and death caused by karma.
Tathagata:
One who has trod the path to full awakening and so reached the end of suffering and escaped samsara; Epithet of the Buddha that he employed primarily when referring to himself.